等离子喷涂 NiCoCrAlY / Al2 O3 涂层的制备及摩擦性能研究

目的制备等离子喷涂NiCoCrAlY/Al2O3高温固体润滑耐磨涂层,并研究该涂层的摩擦性能和磨损机理。方法采用喷雾造粒、化工冶金包覆和固相合金化技术制备NiCoCrAlY/Al2O3复合粉体,用等离子喷涂技术在45#钢表面制备NiCoCrAlY/Al2O3复合涂层。用SEM和XRD等手段分析粉体和涂层的显微结构和物相组成,研究涂层从室温到800℃的摩擦磨损性能,探讨NiCoCrAlY/Al2O3复合涂层在室温和高温下的磨损机理。结果 Al2O3颗粒表面均匀包覆着一层致密的NiCoCrAlY合金,包覆层厚度大约为3~5μm;等离子喷涂NiCoCrAlY/Al2O3复合涂层呈典型的层状结构,涂层各层间结合良好,涂层中孔隙率约为2.84%,主晶相为Ni Cr Al合金相和Al2O3相。涂层的摩擦系数随温度的升高逐渐降低,在室温下约为0.64,800℃时在0.4以下。高温下,金属氧化物的形成是摩擦系数降低的主要原因。涂层的磨损率随温度的升高先升高后降低。涂层在低温下为脆性断裂和磨粒磨损,高温下为氧化磨损、磨粒磨损、塑性变形和金属氧化物的转移。结论等离子喷涂NiCoCrAlY/Al2O3复合涂层是一种性能优良的高温固体润滑耐磨涂层。     

NaF-CaF2-Al2O3-SiO2微晶玻璃的析晶动力学和显微组织

采用传统熔体冷却法制备了掺镱NaF-CaF2-Al2O3-SiO2体系玻璃,并通过优化热处理工艺获得了透明氟氧化物微晶玻璃.通过DSC、XRD和TEM等方法研究了引入碱金属氧化物和碱土金属氧化物对玻璃形成能力的影响,采用动力学方法分析了NaF-CaF2-Al2O3-SiO2系统玻璃的析晶机制,探讨了热处理制度、玻璃析晶行为和显微结构的关系.研究表明:碱金属氧化物的引入降低了该系统玻璃的形成能力,而碱土金属氧化物的添加提高了玻璃的析晶稳定性;该系统玻璃的析晶过程主要受扩散控制,其主晶相为CaF2,析晶活化能为345.8 kJ/mol,晶粒尺寸随晶化温度升高逐渐增大,晶粒数量随保温时间延长逐渐增多.通过优化热处理制度,获得了晶粒尺寸小于50 nm、结晶度约为30%的透明微晶玻璃.     

外熔体温度对7075/6061复合铸锭组织与性能的影响

通过固/液复合铸造技术制备了具有"半固态显微组织/枝晶组织"分布特征的包覆型7075/6061复合铸锭,研究了外熔体温度对该复合铸锭界面组织形态与力学性能的影响规律,探讨了该复合铸锭的界面结合机制。结果表明:外熔体温度760℃、半固态坯料预热温度300℃、保温40 min、空冷条件时,制备的7075/6061双金属复合铸锭的显微组织分布与形态特征较好、抗压强度较高;随着外熔体温度的升高,内层7075合金半固态坯料的近球状α-Al固相颗粒逐渐粗大、球形化逐渐减弱;复合界面处内层半固态坯料局部重熔的现象逐渐增加,界面附近的半固态显微组织形态呈:球状固相颗粒合并长大、非球状化、枝晶化的演变规律;室温压缩时,复合铸锭以圆柱体轴线呈45°角方向裂开,而非复合界面方向。     

催化碳烟氧化用PtCexZr1-xO2催化剂的制备及性能研究

采用水热晶化法一步制备了铈锆摩尔比不同的PtCe_xZr_(1-x)O_2系列催化剂,测定其比表面积、储氧量、氢气还原温度等物化性能参数,并进行结构表征,研究催化剂组成中铈锆摩尔比(n_(Ce)/n_(Zr))对催化剂结构和性能的影响。结果表明,当n_(Ce)/n_(Zr)=5:5时,制备得到的PtCe_(0.5)Zr_(0.5)O_2催化剂晶粒尺寸最小,储氧量较高,氢气还原温度低,微观结构为四方相和立方相2种晶型结构并存的固溶体。与传统贵金属浸渍负载方法制备的Pt/Ce_(0.5)Zr_(0.5)O_2催化剂相比较,水热晶化法一步制备的PtCe_(0.5)Zr_(0.5)O_2催化剂对碳烟的低温氧化具有更优的催化活性。     

一步阳极氧化法制备氧化铝纳米线及其形成机理

采用一步恒压阳极氧化法在草酸电解液中制备氧化铝纳米线,用扫描电子显微镜和X射线衍射仪等对阳极氧化后产物的形貌、晶相进行了分析,研究了氧化电压、反应温度和电解质浓度对氧化产物形貌的影响。结果表明,纳米线的最佳制备条件为40℃、40 V、0.1 mol/L的草酸电解液。新制备的纳米线为无定形结构,在800℃煅烧60 min后转变为立方相氧化铝。同时根据实验结果,从反应界面的温度分布角度,对氧化铝纳米线的形成机理进行了探讨。     

碳钢表面Fe-W-ZrO2纳米复合电沉积层的组织结构分析

采用复合电沉积方法,在碳钢表面制备了质量组成为的Fe 38.3%、W 52.7%、ZrO2-9%的Fe-W-ZrO2纳米复合镀层,研究了ZrO2纳米微粒、热处理对镀层组织和结构的影响.结果表明,弥散分布的ZrO2纳米微粒对Fe-W基质镀层的结构有明显影响,镀态下Fe-W-ZrO2纳米复合镀层内部结构致密无裂纹,呈明显非晶态结构特征;经500℃热处理后,复合镀层开始晶化析出α-Fe相,随着热处理温度升高,晶化相不断析出并长大,700℃时复合镀层晶化已基本完成,M6C型碳化物F3W3C相出现,与α-Fe相两相并存,继续加热至800%:时,F3W3C成为涂层主相.     

Ti60Cu14Ni12Sn4Nb10合金等温退火过程中的相变研究

通过水冷铜模吸铸法制备出了Ti60 Cu14 Ni12Sn4 Nb10复相合金.对合金在不同温度下等温退火过程中的相转变及显微结构演化进行了研究.结果表明,该合金的显微组织主要由β-Ti枝晶相、纳米晶化相和少量非晶相组成.在450℃退火时,合金中有ω-Ti和面心立方结构的Ti形成;而在550℃退火时ω-Ti消失,同时由于非晶相发生了晶化,基体中有TiNi相析出,该晶化相在高于715℃时,转变为稳定的Ti2Ni相;当温度达到795℃时,合金中的β-Ti枝晶相转化为α-Ti.     

焙烧气氛对Ti-6Al-4V合金微弧氧化陶瓷膜相组成影响

在铝酸钠体系中,利用微弧氧化脉冲电源在Ti-6Al-4V合金表面制备了以Al2TiO5为主晶相的陶瓷膜层.试样分别在1000℃下空气和氩气2种气氛中进行焙烧,通过XRD,SEM,XRF等技术分析了陶瓷膜层焙烧前后不同层面的相组成、表面形貌和元素含量变化情况.结果表明:在1000℃空气气氛下,Al2TiO5分解较快,完全分解时,陶瓷膜外层α-Al2O3和金红石相二氧化钛相比例为44:55.而在氩气气氛下,Al2TiO5分解较慢,随反应的不断进行,Al2TiO5含量逐渐减少,完全分解时,陶瓷膜外层为α-Al2O3.膜层由表及里Al2O3含量降低并有Ti2O3生成.焙烧前后陶瓷膜层的形貌变化也不相同,氩气中颗粒较空气中的均匀、细化、孔隙小.膜内元素Ti,Al,P,O的含量在反应前后略有变化.     

旋转浇注法制备AZ91D半固态浆料

采用旋转浇注法制备AZ91D合金半固态浆料,获得了符合金属半固态加工要求的细小、近球状的非枝晶组织.研究表明,适当降低浇注温度、提高旋转管转动速度或采用合适的倾角,半固态组织的初生相颗粒会变得细小、均匀和圆整.在本试验条件下得到的优化工艺参数:浇注温度为630 ℃,旋转管转速为75 r/min,旋转管倾角为25°.     

火花等离子体放电制备高温合金细粉新技术

提出了火花等离子体放电(SPD)制备高温合金细粉新技术,并设计了样机.该方法与常用的高温合金制粉方法一等离子旋转电极法和氩气雾化法的原理不同,与之相比,该方法冷速更快,可制备粒度更细小的粉末,且设备简单.对2种高温合金进行制粉,实验表明:该方法制备的粉末粒度分布窄、球形度高、粉末颗粒表面光滑、看不到枝晶、颗粒内部是球状晶凝固组织,从而组织更均匀.     

Coking by metal dusting of steels

In process industries coking is an annoying phenomenon, the carbon deposition causes decrease of heat transfer and hinders gas flow. Coking in a process may indicate metal dusting, i.e. the disintegration of metals and alloys in carbonaceous atmospheres under formation of graphite and fine metal particles. The metal particles act as catalysts for vast coke formation. The thermodynamics, mechanisms and kinetics of metal dusting have been studied on iron and steels in synthesis respectively reduction gas CO-H₂- H₂O, here the aspects are presented of coking due to metal dusting. From the interplay of the metal disintegration and carbon deposition rather complex coupled kinetics are resulting, even different in a low temperature range where the decomposition of the intermediate cementite is rate determining and in a higher temperature range where the carbon transfer from the atmosphere is rate controlling. Coking by metal dusting can be suppressed in the same way as metal dusting, by sulfur addition to the atmosphere and/or by a stable dense protective oxide layer.     

The solution precursor plasma spray processing of nanomaterials

Solution precursor plasma spray (SPPS) synthesis is a simple, single-step, and rapid technique for synthesizing nano-ceramic materials from solution precursors. This innovative method uses molecularly mixed precursors as liquids, avoiding a separate processing method for the preparation of powders and enabling the synthesis of a wide range of metal oxide powders and coatings. Also, this technique is considered to be promising for the formation of non-equilibrium phases in multi-component oxide systems. This short review provides an insight into the important aspects of SPPS, the properties obtained in comparison to conventional plasma spray, and the potential applications of the SPPS process.     

Oxidation of Two Ternary Cu–Ni–20 wt.% Cr Alloys at 700–800°C in 1 atm O2

Two ternary Cu–Ni–Cr alloys containing approximately 20 wt.% chromium, but with a different Cu and Ni content, have been oxidized in 1 atm of pure oxygen at 700–800°C. The alloy containing about 60 wt.% nickel (Cu–60Ni–20Cr) was composed of a single solid-solution phase and formed external scales of chromium ocide with an outermost layer containing a mixture of copper and nickel oxides. The alloy comprised of about 40 wt.% nickel (Cu–40Ni–20Cr) contained a mixture of two metal phases and formed complex external scales, containing copper oxide and a nickel–chromium spinel plus a region where islands of the metallic phase richer in chromium surrounded by a thin chromia layer were mixed with oxidized islands rich in copper and nickel, producing a situation out of equilibrium. With time, a very irregular and thin but essentially continuous layer of chromia formed at the base of the mixed internal region for this alloy, producing a gradual decrease of the corrosion rate down to very low values. The oxidation behavior of the two alloys is interpreted in terms of their different microstructure. In particular, the fast initial oxidation of Cu–40Ni–20Cr, associated with the formation of large amounts of copper oxides, is attributed to restrictions in chromium diffusion in the alloy due to the simultaneous presence of two metal phases.     

Further aspects of the oxidation of binary two-phase alloys

The corrosion behavior of binary, two-phase alloys is considered in which the matrix contains mostly the less-noble metal that forms a fast-growing oxide, while the second phase is rich in a component that forms a more stable but slowly-growing oxide. It is assumed that the second phase exists as a dispersion of isolated, rod-like particles. It is further assumed that both phases form external films with no internal oxidation. It is shown that the oxidation behavior of this type of alloy depends on both the oxidation time and the size of the second-phase particles. In particular, for short oxidation times and large second-phase particles the matrix will oxidize faster than the dispersed phase, so that the dispersed particles will be only partly corroded or even incorporated into the matrix-oxide scale as unoxidized islands, forming an irregular alloy-scale interface. On the contrary, for long times and small particle sizes the two phases will tend to oxidize at approximately the same rate, leading to the formation of regular alloy-scale interfaces. The time for the transition between the two corrosion regimes depends not only on the ratio between the rate constants for the growth of the two oxides but also on the size of the dispersed-phase particles, smaller sizes producing shorter transition times. Eventually, under favorable conditions the formation of the fast-growing oxide may even stop, leading to the formation of a protective layer of the most-stable oxide.     

金属氧化物半导体纳米晶液相法控制合成研究进展

对金属氧化物纳米晶的晶型、形貌及晶粒大小调控方法进行了综述,重点介绍了液相合成体系中表面活性剂、溶剂、杂质离子等因素对纳米晶形貌、晶型的调控作用以及各种方法的特点,提出发展绿色、高选择性合成方法制备单分散结构可控的金属氧化物半导体纳米晶仍是今后重要的研究方向之一。     

The role of noncrystalline films in the oxidation and corrosion of metals

The role of oxide perfection is a major factor in controlling the rate of oxidation and corrosion of metals. Studies of the reactivity of tantalum, silicon, and amorphous metals are particularly revealing in this regard. Two states of oxide perfection are found: single crystal and vitreous. The former is seldom encountered in practice because it requires epitaxial growth of a single crystal oxide on the metal. However, bond flexibility in vitreous oxides allows them to adapt to various substrates, even polycrystalline ones. Degradation of both single crystal and vitreous oxide results in the formation of polycrystalline oxide. Here, grain boundaries provide paths for easy ion movement and resultant fast oxide growth. Stabilization of vitreous oxide involves bond strength, multiple configurations with equivalent energies, substrate effects, and purity. The control of these factors is the technological challenge to achieving more perfect, and hence more protective, oxides.Invited keynote paper, Session on Amorphous Metals and Films, Fall Meeting of the Electrochemical Society, Los Angeles, California, October 1979.     

不同载体负载的Pd催化剂上CO氧化性能比较

采用沉淀-沉积法制备了一系列不同载体负载的纳米Pd催化剂.以CO氧化为模型反应,考察了载体差异对催化剂CO催化氧化性能的影响.结果发现,载体对Pd催化剂的CO催化氧化性能影响较大,以分子筛为载体的Pd催化剂的活性明显优于金属氧化物担载的催化剂.同时,考察了反应温度、时间、空速及加湿条件等对催化剂CO氧化活性的影响,并利用XRD和XPS等测试手段对催化剂体相结构和表面状态进行了表征.结果表明:催化剂的活性随着反应温度的升高而增加,随着空速的增加而降低.XRD和XPS结果证实不同载体负载的催化剂其表面活性Pd物种的状态有较大差异,分子筛载体利于活性Pd物种向催化剂表面迁移,这种作用以及Pd物种的高分散与催化剂的活性直接相关.     

The Effect of Water Vapour on the Corrosion of Sandvik Sanergy HT Under Dual Atmosphere Conditions

Interconnects of PCFC and SOFC are exposed to dual atmosphere conditions; fuel (e.g. H₂) on the anode side and air on the cathode side. Sandvik Sanergy HT has been investigated under simulated fuel cell conditions at high temperatures. The microstructure and composition of the oxide scales formed at the cathode side (air) were significantly influenced by dual atmosphere conditions. The main effect was a substantial increase of Fe in the oxide scales by the formation of Fe rich nodules accompanied by localized metal loss. The size and number of the nodules increased when introducing water vapour on the air side of the samples. It is suggested that the preferred localization of nodule formation is given by the surface finish as a result of fabrication (e.g. grooves and scratches). By increasing the reaction temperature or duration of the exposures, the effect of dual atmosphere conditions became less pronounced. Alterations to the oxidation mechanism as a consequence of dual atmosphere environments are discussed with basis in the effect of hydrogen permeation through the interconnect alloy. Samples PVD coated with a double layer of metallic Ce and Co were also tested under single and dual atmosphere conditions. No significant change was found in the oxidation behaviour by dual atmosphere exposures.     

Oxidation pretreatment to reduce corrosion of 20%Cr-25%Ni-Nb stainless steel. II. Surface morphology and oxide characterization

Improved corrosion behavior of 20%Cr-25%Ni-Nb steel resulting from a low pressure oxidation pretreatment in CO2 has been related to changes in elemental composition and distribution in the oxide scale. Auger electron spectroscopy, secondary ion mass spectroscopy, electron microprobe, and X-ray diffraction techniques have been used to investigate the properties of the oxide scale formed on both untreated and pretreated specimens when oxidized at 823 K and 923 K in a CO₂-1%CO atmosphere. A sputter ion plating technique has been used to separate the oxide from the metal and the incorporation of chromium and silicon at the metal-oxide interface has been investigated at grain centers and grain boundaries by depth profiling. The improvement in oxide adhesion and oxidation rates, using data from Parts I and II of this study, is assessed in terms of oxide formation by solid-state displacement reactions.     

纳米复合电刷镀层微观组织及其成形过程中的氧化现象

研究了n—Al2O3／Ni纳米复合刷镀层的微观组织及其成形过程中基质金属镍的氧化现象。结果表明：复合刷镀层晶粒细小，n—Al2O3颗粒在复合刷镀层中弥散分布；在刷镀过程中，生成了大量氧化镍，它以单独的NiO颗粒形态或生成的NiO和加入的Al2O3的球形颗粒混合体形态分布在复合刷镀层晶簇内部及晶簇边界区域。提出了NiO的形成机制，即主要通过如下3种途径：①新生成镀层表面镍原子与镀液薄膜中溶解氧发生化学反应；②镍离子与溶解氧，发生电化学反应；③在碱性溶液环境中纳米颗粒表面吸附[OH]^-发生电化学反应生成NiO。